Tried something else today, something with a very simple shape and texture so I would be able to just test if I can get it into the game at all....
Turns out textures can't be positioned in any way, in Unity. So although I feel it's totally backwards, the shape and the texturemapping is done in Blender and any materials are added in Unity. Not at all confusing.
Next, according to the tutorial for Founder's Fortune, you open a specific asset/tool they have set up, which they call photoStudio. This is to make in game icons of the item. I found the tool. I somehow managed to choose one of several pre-arranged cameras, which should be suitable for my item. (Edit: after this moment I have been completely unable to switch to another camera set.) It wasn't, so I managed to adjust the view. Then one was to use the game window and "in the top bar set the resolution to something square". Well, after looking for quite a while and tearing my hair and cursing a bit I found a place to do that. No, it wasn't obvious. Now, there's a kind of pop up window with instructions on what to do, in the game window, obscuring the view. In this window it says to enter a name for your icon. But you can't enter anything or even activate the entry field with the cursor. And then there's a snap photo button, which also doesn't do shit. Which means I can't even take a screenshot of the item in the right orientation with an easy to edit plain gray background because the popup or overlay thingy is in the way.
I figured maybe the photo thingy was frozen for some reason so I quit the program and restarted. Well, tried to. One try, there's no such project, next try the API files (from mere minutes ago?) are too old, next it just crashes without knowing why and when it finally opened again (after I also tried restarting the computer) it opened in photoStudio, which is still useless and now I don't know how to get back to my previous stuff.
I also tried taking the screenshot for the icons in Blender but there I can apply texture, adjust camera and what not, but not actually see a rendered image?
I must be such a total idiot.
Maybe it's time I gave Creedfall another try. I played it once, this morning (around 6 am when I couldn't sleep) and I didn't even make it out of port before I died (the whole premise is that you're leaving for a mysterious island...)